Aluminum 8090: Composition, Properties, Temper Guide & Applications

Comprehensive Overview

8090 belongs to the 8xxx series of aluminum alloys, a family characterized by the presence of lithium as a primary alloying addition. These alloys are developed to yield a favorable strength-to-weight ratio and increased elastic modulus by incorporating Li at levels sufficiently high to reduce density and modify the precipitation spectrum relative to conventional Al-Cu/Mg systems.

The major alloying elements in 8090 typically include lithium, copper and magnesium with small additions of zirconium and trace elements to control recrystallization and grain structure. Lithium lowers density and increases modulus, copper and magnesium provide age-hardening through precipitation, and zirconium or titanium are added as grain-refiners and to produce a fine dispersoid population that stabilizes the microstructure against over-ageing.

8090 is a heat-treatable alloy that gains strength principally through solution heat treatment, quenching, and artificial aging to produce dispersions of fine precipitates (typically T1-, δ′- and S-type intermetallics depending on chemistry). The alloy combines elevated specific strength with improved fatigue crack growth rates and modest corrosion resistance compared with many high-strength 2xxx alloys, making it attractive where mass savings and high structural performance are required.

Typical industries for 8090 include aerospace primary and secondary structures, high-performance ground transportation (where weight is critical), and specialized military or space hardware. Engineers choose 8090 over other alloys when the design prioritizes a high specific strength and stiffness, reduced part mass, and fatigue resistance even when that choice requires narrower processing windows and more careful corrosion control.

Temper Variants

Temper	Strength Level	Elongation	Formability	Weldability	Notes
O	Low	High (20–30%)	Excellent	Excellent	Fully annealed, best for forming and joining
T3	Medium-High	Medium (10–18%)	Good	Moderate	Solution treated, cold worked, natural aged; balanced properties
T4	Medium	Medium-High (12–20%)	Good	Moderate	Solution treated and naturally aged; intermediate strength
T6	High	Low-Medium (6–12%)	Limited	Challenging	Peak artificial aging; highest common static strengths
T8	High	Low-Medium (6–12%)	Limited	Challenging	Solution treated, cold worked, and artificially aged for improved toughness
T86	High	Low-Medium (6–12%)	Limited	Challenging	T8 variant with controlled stabilization to limit property drift
H1x / H2x	Varies	Varies	Varies	Good	Strain-hardened states applied to sheet/extrusion for specific form/strength

Temper selection in 8090 strongly influences both static and cyclic performance because the precipitation sequence and dispersoid distribution are temperature- and deformation-sensitive. Peak-aged tempers (T6/T8/T86) provide the highest tensile and yield strengths but at the cost of ductility and formability; annealed or lightly aged tempers are used where forming or joining take priority.

Chemical Composition

Element	% Range	Notes
Si	0.05–0.20	Controlled low silicon to minimize brittle intermetallics and retain toughness
Fe	0.05–0.25	Kept low to avoid coarse intermetallic particles that reduce fatigue life
Mn	0.02–0.15	Minor element; can influence grain structure and corrosion behavior
Mg	0.3–1.0	Combines with Cu to promote age-hardening precipitates and strengthen matrix
Cu	2.0–3.0	Primary strengthening element through precipitate formation (T1, θ′-like phases)
Zn	0.05–0.50	Kept low; higher Zn can promote strength but increases SC susceptibility
Cr	0.00–0.10	Trace levels for grain boundary control and to limit recrystallization
Ti	0.00–0.10	Added for grain refinement in cast or wrought products
Li	1.6–2.5	Primary feature of the alloy family; reduces density and increases modulus
Zr	0.05–0.25	Added to form fine Al3Zr dispersoids that pin sub-grain structure and resist grain growth
Others	Balance Al, traces	Trace elements (B, Ca, Sr) used in manufacturing control; consult supplier spec

The listed ranges are typical production windows and will vary by producer and product form; users must consult mill certificates for exact chemistries. Lithium and copper dominate performance: Li lowers density and increases modulus while Cu and Mg determine the precipitation hardening response; Zr and Ti control recrystallization and the stability of the aged microstructure.

Mechanical Properties

In tensile behavior 8090 shows a pronounced increase in both yield and ultimate tensile strength with artificial aging, while the annealed states maintain significant ductility and formability. Yields in peak-aged tempers are substantially higher than in annealed or naturally aged states but can be accompanied by reduced work-hardening capacity and tighter limits on allowable deformation prior to cracking.

Hardness correlates closely with the aging condition and with thickness due to quench sensitivity; thin gauges typically reach higher retained strengths after quench-and-age than thick sections. Fatigue resistance of 8090 is generally better than many 2xxx series alloys at comparable static strength due to a finer precipitate and dispersoid architecture that slows crack initiation and early propagation.

Thickness and product form affect both mechanical properties and achievable temper. Thick plates and extrusions are more susceptible to quench-induced softening in the interior and require modified heat treatments and/or overaging controls to achieve homogeneous properties through section.

Property	O/Annealed	Key Temper (e.g., T6/T8/T86)	Notes
Tensile Strength	160–240 MPa	420–520 MPa	Peak-aged strengths vary with exact chemistry and thickness
Yield Strength	60–140 MPa	340–420 MPa	Yield/tensile ratio tightens in high-strength tempers
Elongation	18–30%	6–12%	Ductility drops substantially as strength is increased
Hardness (Vickers)	35–50 HV	120–150 HV	Hardness increases mirror tensile strength changes; thickness-dependent

Physical Properties

Property	Value	Notes
Density	~2.62–2.66 g/cm³	Reduced relative to conventional Al alloys due to Li content
Melting Range	~500–655 °C	Solidus–liquidus range dependent on minor alloying; aluminum base ~660 °C
Thermal Conductivity	~110–140 W/m·K	Lower than pure Al and some 6xxx alloys; conductivity decreases with alloying
Electrical Conductivity	~28–38 % IACS	Reduced by alloying elements and precipitation state
Specific Heat	~0.85–0.92 J/g·K	Similar to other Al alloys at ambient temperature
Thermal Expansion	~21–24 ×10⁻⁶ /K (20–100 °C)	Slightly lower CTE than many Al alloys because of Li; good for some dimensional stability needs

The lower density of 8090 yields direct mass savings in structural components and contributes to improved specific modulus. Thermal and electrical conductivities are moderate in comparison with high-purity aluminum; design must account for reduced thermal conductivity in heat-sink applications. The slightly reduced coefficient of thermal expansion improves dimensional stability in assemblies where thermal cycling is important.

Product Forms

Form	Typical Thickness/Size	Strength Behavior	Common Tempers	Notes
Sheet	0.3–6.0 mm	Good uniformity in thin gauges	O, T3, T6, T8	Widely used for formed skins and fuselage panels
Plate	6–50+ mm	Strength may be reduced in thick sections due to quench sensitivity	T6 variants, T86	Requires specialized quench and aging schedules for homogeneity
Extrusion	Complex profiles	High directional strength along axis	T3, T6, T8	Used for structural rails, stringers; microstructure elongated by extrusion
Tube	1–25 mm wall	Good axial properties	T6, T8	Hydroformed tubes can be used in weight-sensitive frames
Bar/Rod	Φ5–150 mm	Good mechanical anisotropy along length	T6, T8	Machined fittings and fastener blanks

Processing route and product form determine achievable properties; cast-to-wrought transitions are rare for Al-Li; most 8090 products are wrought and require careful control of solution treatment and quench rates. Thin-products typically reach higher retained strengths after aging because of faster quench rates, while thick-products require modified thermal cycles or post-process mechanical treatments to ensure property uniformity.

Equivalent Grades

Standard	Grade	Region	Notes
AA	8090	USA	Recognized by major North American producers; supplier-specific variants exist
EN AW	—	Europe	No single harmonized EN equivalent; similar Al-Li alloys are used (consult mill)
JIS	—	Japan	Localized Al-Li alloys exist; direct JIS equivalent not commonly standardized
GB/T	—	China	Chinese standards include Al-Li alloys with comparable chemistries but not always a direct 1:1 match

Because 8090 is a specialized Al-Li composition, there is no universal international one-to-one equivalent; regional producers often supply alloys with slightly different Li/Cu/Mg balances under proprietary designations. Engineers must compare chemistry and temper response rather than relying solely on nominal grade numbers when substituting materials across suppliers or geographies.

Corrosion Resistance

In atmospheric environments 8090 exhibits acceptable general corrosion resistance comparable to many heat-treatable aluminum alloys when properly surface-treated. The presence of Li and Cu requires controlled surface preparation and protective coatings because copper can promote localized corrosion in aggressive environments; anodizing and modern conversion coatings are commonly used.

Marine behavior is reasonable for structures that are painted or sealed, but bare 8090 in salt spray or splash zones will show increased susceptibility to pitting relative to some 5xxx series magnesium-bearing alloys. Proper design to avoid crevices, control residual stresses, and isolate dissimilar metals is essential in coastal and offshore applications.

Stress corrosion cracking risk exists for high-strength tempers, particularly in environments that supply cathodic reactants or where galvanic coupling accelerates local damage. 8090 generally resists SCC better than certain 2xxx families due to its precipitate distribution, but it is not as intrinsically SCC-resistant as many 5xxx series alloys; design mitigation and post-weld treatments are common practice. Galvanic interactions with stainless steel or carbon-fiber composites require insulating barriers or sacrificial anodes to prevent accelerated corrosion.

Fabrication Properties

Weldability

8090 is more challenging to weld than non-heat-treatable alloys due to lithium’s effect on weld metal porosity and the propensity for hot cracking in high-strength Al-Cu systems. Fusion welding (GTAW/MIG) can be performed on O or overaged tempers with care; however, high-strength tempers lose hardness in the heat-affected zone and post-weld repair or localized heat treatment is often necessary. When welding is required, matching filler alloys designed for Al-Li systems or low-susceptibility Al-Mg fillers are recommended, and pre- and post-weld thermal-mechanical procedures should be specified to control distortion and property loss.

Machinability

8090 has machinability similar to other high-strength Al alloys; it machines reasonably well with carbide tooling but is more abrasive than high-purity alloys due to hard dispersoids and intermetallic particles. Recommended cutting speeds are moderate with robust chip-breaking strategies; coolant and chip evacuation are important to avoid built-up edge and workpiece heating. Tool geometry favoring positive rake angles and high feed rates with low depth-of-cut typically produce the best surface finishes and tool life.

Formability

Forming 8090 is most effective in the annealed or lightly aged tempers; the alloy has limited stretch formability in peak-aged conditions and is prone to cracking if deformation exceeds ductility limits. Bend radii should be generous in high-strength tempers—typical minimum bend radii are several times the sheet thickness depending on temper and direction. Where severe forming is required, solution-treatment and controlled tempering or incremental forming methods can be employed, and warm-forming strategies can improve ductility for some geometries.

Heat Treatment Behavior

8090 is heat-treatable and responds to solution treatment and artificial aging sequences that produce fine, coherent precipitates. Typical solution treatment temperatures fall in the mid-500 °C range depending on section size and chemistry; solution hold and rapid quench are critical to minimize coarse precipitate formation and to retain solute for subsequent aging.

Artificial aging is commonly performed in the 120–190 °C range for Al-Li alloys; peak properties are achieved through precise time-temperature schedules (T6/T8 family) that balance the formation of strengthening phases with retention of adequate toughness and corrosion resistance. Overaging can be used in some applications to improve stress-corrosion resistance and toughness at the expense of peak strength, and T86-style stabilized tempers are used to hold properties during service.

Non-heat-treatable strengthening is not the primary path for 8090, but cold work following solution treatment and prior to aging (T8) is a standard practice to raise yield strength and enhance fatigue performance through strain-induced nucleation of strengthening precipitates.

High-Temperature Performance

8090’s usable temperature range for load-bearing applications is generally limited to well below typical aging temperatures; sustained exposure above ~150–175 °C leads to progressive softening and loss of peak-aged strength. Elevated temperature exposure accelerates precipitate coarsening and the dissolution of fine strengthening phases, reducing both static and fatigue properties.

Oxidation at service temperatures is minimal because aluminum forms a protective Al2O3 scale; however, high-temperature environments with aggressive chemical species can degrade protective films. The heat-affected zone from welding is especially vulnerable to over-ageing and residual stress-driven degradation when components are exposed to transient high temperatures.

Applications

Industry	Example Component	Why 8090 Is Used
Aerospace	Fuselage skins, floor beams, structural fittings	High specific strength and stiffness with weight savings
Marine	High-performance hull components and hardware	Improved strength-to-weight; suitable with coatings and isolation
Aerospace/Military	Stringers, frames, landing gear fittings (secondary)	Fatigue resistance and reduced mass for dynamic loads
Electronics	Lightweight structural housings	Good strength-to-weight and dimensional stability

8090 is selected in designs where every kilogram saved yields system-level performance advantages and where controlled processing and finish systems can mitigate environmental or fabrication-driven weaknesses.

Selection Insights

Use 8090 when mass reduction and high specific stiffness are primary requirements and manufacturing facilities can control heat treatment, quench, and corrosion protection. It excels where fatigue resistance per unit mass is critical and where the higher procurement and processing overheads can be justified by performance gains.

Compared with commercially pure aluminum (e.g., 1100), 8090 trades electrical/thermal conductivity and forming ease for substantially greater strength and modulus. Compared with common work-hardened alloys (e.g., 3003 / 5052), 8090 provides much higher peak strength and better fatigue crack growth resistance but requires more careful corrosion protection and is less formable in high-strength tempers. Compared with ubiquitous heat-treatable alloys (e.g., 6061 / 6063), 8090 often delivers superior specific strength and stiffness despite similar or slightly lower absolute peak strengths; choose 8090 where mass and modulus are decisive and supplier capability for Al-Li processing is available.

Closing Summary

8090 remains relevant where high specific strength, improved stiffness, and fatigue performance justify tighter processing controls and protective measures. When used with appropriate temper selection, surface protection, and fabrication practices, it provides an effective path to lightweight, high-performance structures in aerospace and other weight-sensitive industries.